As digital communication becomes more commonplace, the need for securing the communication channels becomes increasingly more important. For example, current technologies allow a user to remotely access bank accounts, medical information, and other private and sensitive data.
Cryptology has been widely used to provide secure digital communication. Cryptology relates to the enciphering (or encrypting) and deciphering (decrypting) of messages. The encryption and decryption generally uses some secret information (such as a key) for processing the data to be secured. In different encryption methods, a single key or multiple keys may be used for encryption and/or decryption.
Currently, two types of symmetric cipher are in common use. Generally, the encryption is said to be symmetric-key if for each associated encryption/decryption key pair, it is computationally “easy” to determine each of the keys in the key pair from the other key in the key pair. The first type of symmetric cipher is a block cipher which operates on a large block of data. The second type is a stream cipher which, by contrast, operates on relatively smaller units of text (such as bits). Depending on its implementation, stream cipher is believed to be much faster than block cipher and, hence, of special interest.
Additionally, stream ciphers can generate streams (also known as a “keystreams”) while approaching the high security of one-time pad. Generally, one-time pad cipher generates a keystream with the same length as the text message being encrypted. The one-time pad keystream is believed to be completely random, yielding very high security levels.
One of the most widely used stream cipher techniques is the alleged RC4 (Ron's Code 4—variable-key-size encryption algorithm by Ron Rivest of RSA (Rivest, Shamir, and Adleman public key encryption technology)). For example, the alleged RC4 is used in SSL (secure socket layer) which is implemented in many Internet-based communications (e.g., through HTTP (hyper-text transfer protocol) and FTP (file transfer protocol)).
The alleged RC4, however, can require eight to sixteen machine cycles to output a single byte. While this can be run in software, it requires a substantial amount of hardware resources. Also, implementing the alleged RC4 in hardware limits the flexibility of running the alleged RC4 on different computing devices (i.e., because it would require the presence of alleged RC4-specific hardware in each device).
Another method used for securing data is a hash function. A hash function transforms an input string into a fixed-size output string (also known as a “hash value”). The size of the output string is referred to as a message “digest.” It is generally desirable to provide a hash function that is one-way (i.e., hard to invert) and collision-free (i.e., different hash values are generated for different messages). One standard hash function is SHA-1 (secure hash algorithm as revised in 1994) which generates a 160-bit digest from an input stream of less than 264 bits.
Cryptographic primitives such as stream ciphers and secure hash functions are an essential part of many cryptosystems, making their efficient computation an important problem. Most practical implementations, however, use custom designs (message digests (e.g., MD5 and MD6), SHA-1 or alleged RC4, Seal, and Scream) that depend on empirical analysis, as opposed to formal complexity theoretic or information theoretic analysis.
Accordingly, the current solutions fail to provide an efficient methodology for quick and secure data encryption/decryption, while maintaining sufficient efficiency and/or speed for implementation in software.